Extruded sheet material



Dec- 15. 1970 oLE-BENDT RASMUSSEN 3,5@7'763 EXTRUDED SHEET MATERIAL 2Sheets-Sheet l Filed Dec. 29, 1968 I NVENTOR BY MW ATTORNEY i5 l@v@LE-BENIN RASMUSSEN www EXTRUDED SHEET MATERIAL 2 Sheets-Sheet FiledDec. 29, 1968 INVENTUR ATTORNEY United States Patent (Milice 3,547,761Patented Dec. 15, 1970 3,547,761 EXTRUDEDv SHEET MATERIAL Ole-BendtRasmussen, Topstykket 7,

Birkerod, Denmark Filed Dec. 29, 1967, Ser. No. 694,660 Int. Cl. B321)/16, 5/18, 9/00 U.S. Cl. 161-168 14 Claims ABSTRACT OF THE DISCLOSUREThe present invention relates to an extruded sheet material consistingof a polymeric reinforcement material and a filling material.

The combination of reinforcing material and filling material in a sheetis usually made by simple compounding before the formation of the sheet,or by using the reinforcement material in the form of a woven, knittedor non-woven fabric to which the filling material is adhered, or bylaminating the filler to one or several films of the reinforcementmaterial. In the first case the reinforcement material is substantiallyweakened at least with respect to creep resistance, whereas theproduction of the second kind of sheet material is relativelycomplicated and expensive, and the third kind of sheet materialgenerally has low abrasion resistance or a tendency to delamination onbending. The present invention has for its object to over come theabove-mentioned drawbacks by use of' the reinforcement and fillingmaterials in a new, suitable laminated arrangement which easily can beproduced by extrusion.

In the extruded sheet material according to my invention a reinforcingpolymeric material and a filling material are present in the sheetmaterial in the form of interspersed intimately adhering thin lamellae,the former having an overall thickness between 0.1 and microns andtraversing vthe flat dimension of the sheet at an' overall angle of lessthan 2 to the surfaces of the sheet. The said range of thickness isactually about the marginal range between dimensions which with regardto dispersions are considered to be colloidal, and dimensions which inthe same respect are considered to be macrodimensions. Probably as aresult of the fact,`that a reinforcement material and a filling materialhave very different mechanical characteristics, it has been found that alaminate of such materials tends to behave more and more as anundisruptable whole when the thickness of the layers of the formermaterial approaches or reaches colloidal dimensions. If, on the otherhand, the thickness of the reinforcement layer gets really down incolloidal dimensions, surface irregularities-will play an essential roleto weaken the material. The `indicated range of thickness has been foundgenerally suitable, andY more particularly, the range between 0.5 micronand 5 microns is generally preferable. The use of the colloidal oralmost colloidal thickness of the layers has a further advantage in thatlocal failures in-the raw materials as well as scratches in the surfacemade by abrasion, have very littlev influence on the tensile strength ofthe sheet. It would be very difficult and uneconomical to produce,handle and laminate film material of such fine thickness in conventionalmanner in order to make laminates of the thickness which is generallyrequired for packaging and other purposes. However, the inventionprovides a practical and economical method of making a sheet material ofthe kind described, said method comprising feeding fluid firstextrudable, polymeric material suitable to form said reinforcementmaterial to first orifices in a row of orifices in an extruding device,feeding a fluid second extrudable material suitable to form said fillingmaterial to second orifices in the row, extruding the fluid materialsthrough the orifices into a collecting chamber that extends along thelength of the row and has an outlet slot extending along the length ofthe row, and while extruding said fluid materials through saidcollecting chamber and slot, subjecting the extruded sheet to atransverse smearing action.

If the thickness of the lamellae is not sufficiently reduced during thepassage through the extruding device, the sheet material must be drawnsubsequently in one or several operations.

The transverse smearing out, by which the lamellae of the material arebrought down to at least a relatively fine thickness, if not fullybrought down to the final thickness of between 0.1 and 10 microns, canbe established by movement of the chamber and the row of orificesrelative to and along one another. In this case the collecting chambershould preferably narrow down immediately after the orifices preferablyin a neck, i.c. very rapidly in order to enable a sufficient shear to beproduced between the nozzle parts in the row and the Walls of thecollecting chamber. The extruded lamellae are hereby deflected from theforward direction and will continue their flow in a broadside manner.The broadside flow through the collecting chamber and the slot at itsend will make the lamellae drag in the direction of extrusion, i.e. thesides of the lamellae will be dragged in relation to their centralportion.

An alternative method of establishing the transverse smearing out is tomove one side of the collecting chamber relative to and along the other.The sides of the lamellae will thereby be dragged in relation to eachother. In this case it is less important for the collecting chamber tonarrow down, and there may even be a long chamber zone, where notransverse shear occurs, between the row of orifices and the moved partsof the collecting chamber, since the nozzle parts need not partake inthe smearing action in this case. However, it is also possible tocombine the two methods.

The orifices for extrusion of a large number of lamallae side by sideinto the collecting chamber are preferably closely spaced, elongatedslots forming an angle with the row in which they are arranged.

It seems impossible to make the spacing between the extrusion orificesof the row closer than about 1 mm., and generally at spacing of 2-3 mm.is preferable for constructional reasons. If the extrusion velocities ofthe two polymeric materials are equal, the original thickness of thelamellae will equal the distance between the slots, however it is easyto obtain the desired small thickness of the lamellae by the draggingand shearing action described.

I use the term lamellae to signify any body in which one dimension isVery much greater than one at least of its other dimensions, and in myfinal product at least one dimension is very much less than the othertwo dimensions.

The conformation of the lamellae will depend upon Y the manner offorming the sheet material. If there is of extrusion. The centralportion of the U purposely may be missing as Will be explained in afollowing paragraph.

If one side of the collecting chamber is moved relative to the other asthe lamellae are passing through it this will drag the sides of thelatter with the effect that the lamellae of first polymeric material'will be brought to lie substantially parallel to the plane of the sheetmaterial. I call the shape of the lamellae, in the direction transverseto the length dimension of the lamellae, a flattened S in this instance.It is also possible to chop the lamellae into shorter lengths, beforethe final shear or dragging action in the extrusion device, and thediscontinuous lamellae hereby will form rows of U or S profiles in theextruded sheet material.

The shape of the lamellae will depend at least in part upon theproportion between the viscosities of the particular polymeric materialsthat are used as Well as their deviations from Newtonian behavior, andupon the movements and shape of the devices establishing drag and shear.

Generally the materials should have rather similar viscosities, but theuse of different viscosities is facilitated by making a sudden reductionof the thickness of the extrusion nozzle at the orifices, so that asubstantial pressure drop is produced within the orifice.

It is sometimes desirable to draw the lamellae in two steps while theyare fluid. This may be achieved by supplying the collecting chamber witha larger number of dividing walls after the neck so as to form in thecollecting chamber a row of channels parallel to the row of extrusionorifices, and feeding the fluid lamellae material emerging from thechannels into a second collecting chamber that also extends along therow. This second chamber preferably has a similar internal prole as thefirst a-nd preferably also includes a neck leading to its slot. Thischamber as well as the row of extrusion orifices by which the lamellaeare originally formed are preferably stationary with respect to the rowof slots, whereas the first collecting chamber is reciproeated orrotated.

In general, I prefer to extrude the lamellae through a circular row ofslots, the collecting chamber then being a correspondingly circularcollecting chamber. The rotating devices lcan either be arranged forproduction of the S-form, or the U-form, or a mixed form between the Uand the S.

The product obtained on rotating the collecting chamber as a wholerelative to the circular row of slots Will have the lamellae arranged asa helice in the extruded tube. The pitch angle of the helice will dependon the relative speeds of rotation, but in case the lamellae are madecontinuous and the process takes place without any movement of the twoparts of the collecting chamber relative to each other, the helices mustnecessarily become very flat in order to obtain a sufficiently smallthickness of the lamellae.

In case the die-lips from which the fluid sheet material is hauled offis rotated as a whole, the nip of the haul-off rollers must beconstructed to rotate in similar manner. As an alternative to therotation of the dielips, the part of the device containing the row ofextrusion orifices may be rotated, in 'which `case the main channelsfeeding the extrusion orifices will have to be connected to theextruders through suitable concentric revolving fittings.

If the row of slots and collecting chamber are both linear the movementbetween the chamber and the slots, or between one side of the chamberand the slots has to be reciprocal, with the results that the lamellaewill be folded back and forth upon themselves.

Comparing the effect of the different forms of the lamellae, the S-form,or those mixed forms which are predominantly S-formed, generally aremore suitable than lthe U-'form and those mixed forms which arepredominantly U-forrned. This is due to the fact that in a certain,central layer of the sheet of U-formed lamellae the latter graduallychange their angle of traversing from the indicated marginal value o-f 2to 90 and back to 2 at the same time as the thickness of the reinforcinglamellae generally will be greater than the indicated margin of 10p atleast within a portion of this layer. Such deviations in a central layerdecrease the strength. If, however, the sheet of U-shaped lamellae(hereunder mixed forms still having a U-like cross-section) is cleavedthrough the core, the resulting sheets, in which the lamellae have theform of a split U, hereinafter called the l-form, will have improvedabrasion resistance on the surface iwhich formerly was in the core, nowhaving the lamellae arranged in a kind of pile intimately adhering tothe filling material. This cleavage can with advantage take place duringhaul-off by means of a blade inserted into and parellel to the long slotof the extrusion device, but it can also take place after hauloff bymeans of a band saw or the like.

However, the preferable way of making such cleaving, particularly withview to production of the I-form, is to avoid extrusion of thereinforcing material in a core layer of the sheet material. Thisembodiment is carried out by use of an extrusion device, in which rstorifices are located in zones on both sides and spaced from a lineparallel to the margins of the row of orifices. Because of the lack ofreinforcing material in a core layer, the cleaving will be very muchfa-cilitated, and can often Ibe carried out by simple peeling. In casethe filling material has lower melting point than the reinforcementmaterial, peeling preferably is carried out at a temperature where thefilling material is fluid or semi-fluid, but the reinforcement materialis solid.

As mentioned, the surface formed by cleavage generally exhibitsincreased abrasion resistance because it consists of reinforcinglamellae portions in pile-like arrangement, connected by the fillingmaterial. If, however, the abrasion resistance is of less importance,but high tensile strength is aimed at, the lamellae portions near thecleaved surface are preferably smeared out by rolling in fluid orsemifluid state. The J-form will hereby be converted to an S-form.

While the directly formed S-lamellae generally are longitudinallydirected in the sheet, the V and J lamellae as well as the S-lamellaeformed via the I-form generally will be directed practically laterally.In any case, it will normally be preferable to use lamellae which arecontinuous over one of the principal directions of the area of the sheetmaterial, whereas the chopped lamellae arranged in rows may beadvantageous in cases where, because of a particular choice ofmaterials, it m-ay be diflicult to obtain sufficient fineness of thelamellae by a one-step smearing-out, or in cases Where the fillingmaterial is a porous material, and it is desirable to give thereinforcing material a slightly discontinuous structure in order toallow a certain passage of liquids or gases through the material.

The sheet material according to the present invention may compriselamellae of at least one further extrudable material interspersed withthe lamellae of reinforcing material and the lamellae of fillingmaterial. This may be an adhesive suitable for. bonding the lamellae ofsaid reinforcing and filling materials together, such as, for instance,a mixtureof tfe principal polymeric components of said reinforcing a dfilling materials, or a graftor block-copolymer of both. Of thesepossibilities, the graftor block-polymers generally exhibit the bestcohesive strength, whereas the mixture generally is cheaper. In order toincrease the cohesive strength of the said mixture, the componentsshould have relatively high molecular weight and should be relativelysoft modifications of the respective polymers.

The adhesive material or other material or materials interposed betweenthe reinforcing lamellae and the filling lamellae are injected by meansof a separate extruder or extruders through separate channel system orsystems to a separate set or sets of extrusion orifices in the row oforifices of the extrusion device. It is within the scope of theinvention to arrange the sheet with several different reinforcingmaterials and/or several different lling materials in the form ofseparate sets of lamellae. In actual fact, the extrusion device maycomprise a rather great number, say 7, of separate channel systems andcorresponding sets of orifices.

In order to obtain the highest possible strength, the reinforcingmaterial should generally be a crystalline polymeric material, andwhenever possible, the latter should preferably be oriented.

In one embodiment of the present invention, said filling materialconsists of a mixture of inorganic solid particles and a polymericbinder therefor. Such material may be particularly cheap. Saidinorganic, solid particles may, for instance, be carbon, or talc, orwater-insoluble oxides, sulphates, silicates, carbonates or sulphidesnormally used as filling material.

In another embodiment of the present invention, said filling material isa cellular polymeric material. In this form of the invention, there isobtained a combination of strength and volume which for instance makesthe material suitable for bookprint paper and several kinds of wrappingmaterial. The volume facilitates the handling of thin sheet materialthrough an increase of stiffness, and with regard to packaging uses thematerial is suited for protection against impact actions. Because of thevery limited number of actually available polymer substances for makingcellular products, it Iwill normally be diflicult to find suitablecombinations of reinforcing material and cellular material which arecapable of uniting directly, thus it is normally necessary to interposea set of adhesive lamellae. The expansion to form the cellular structurecan take place by well-known methods either during haul-off or laterhowever the last mentioned possibility seems to be preferable in mostcases, as the expansion tends to weaken the reinforcement lamellae whencarried out while the latter are fluid. The lamellae of reinforcementmaterial may, in fact, facilitate the expansion by setting up a barrieragainst diffusion of the expansion agent. The materials may be selectedwith regard to this effect.

When this embodiment of the invention is applied to make substitute ofbookprint paper or for other very lightweight` purposes, it maybepreferable to obtain the desired small thickness by cleaving a thickersheet according to the invention along at least one plane parallel toits surface. This can be done with use of cleaving apparatus known fromthe leather industry. t p

A suitable combination of materials for the embodiment of te invention,in which the filling material is cellular, is polyethylene asreinforcement material, cellular polystyrene as the filling material,and an adhesive material being interposed. l

In another embodiment of the present invention, `the lamellae of thefilling material comprise a split-fibre net- Work. This provides for amaterial of high absorbing power. Suitable materials for producing suchsplit-fibre networks are well known in the art. ItV should beunderstood, that the term split-fibre networks also comprises fibres inthe form of needleto threadformed crystal formations of a crystallinepolymerbunched together to a network structureeven when the splittinghas been carried out without any molecular orientation beingpresent.

In a further development of this embodiment also the reinforcementmaterial comprises split-fibre network material, however, of higherstrength and lower average fibre fneness than that forming the lamellaeof the filling material. In this form, the product is suitable aslayer(s) in non-woven fabric or even as an independent non-woven fabriceither for disposable apparel, table cloth, window curtains and thelike, or for sanitary textiles or filter materials, The methods ofproducing the fibrous networks by suitable choice of ra'w materials(generally intimate mixtures of different polymers) and by processessubsequent to the extrusion of the sheet (such as drawing and swellingand/or leaching) can easily be carried out by an expert by adaption ofthe known art.

In still another embodiment of the present invention, the reinforcinglamellae consist of crystalline, oriented polymeric material, whereasthe filling material has a higher flexibility than the reinforcingmaterial. This material has a surprising overall strength and is verysuitable for heavy duty bags, for different kinds of wrapping materialand for many other purposes, where in particular a combination oftensile strength, flexibility, initial tear strength, tear propagationstrength and impact strength is required. It appears that the flexiblelamellae are very suitable for smoothing out the force actions oftearing and for absorbing shock actions.

Said flexible filling material can, in order to establish the intimateadhesive bonding, be a co-polymeric modification of the principalpolymeric component of the reinforcement material. Thus it can, withgreat advantage, be a block-copolymer containing segments of theprincipal polymeric component of the reinforcing material and segmentsof an elastomer, or alternatively, a graft-polymer having branches ofthe principal polymeric component of the reinforcement material graftedupon an elastomeric backbone.

In case the more flexible filling material is orientable, it shouldpreferably not be in oriented state in the end product as it ought toexhibit a high ability to yield without breaking. Thus, when the meltingrange of this filling material is below the melting range of thereinforcement material, as it will normally be, the orienting may becarried out while the filling material is fluid but the reinforcementmaterial is solid, or alternatively, the sheet may be annealed at asuitably high temperature subsequent to the orienting in order todestroy the orientation of the filling material but not that of thereinforcement material.

The lamallae of filling material may extend beyond the lamallae ofreinforcing material to form at least one surface layer of the sheet.This is often useful, when the filling material has a lower meltingrange than the reinforcing material, as it enables sealing together oftwo sheets without ruining the orientation in the reinforcing lamallae.This extension of the lamallae is obtained by making the orifices in therow extend correspondingly one set beyond the other. However, a materialsuitable for the flexible filling lamallae will often be too sticky forbeing suitable as a surface layer. It is preferable to intersperse withthe lamellae of reinforcing and filling material lamellae of acrystalline polymeric material having a substantially lower meltingrange than the reinforcing material. This lower melting, crystallinematerial should be adjacent at least one surface and extend beyond bothto form at least one surface layer of the sheet. Because of its lowermelting range it serves the sealing of the material, and because of itscrystallinity it is non-sticky and will exhibit a suitablecohesivestrength. Preferably this surface material should only overlapthe adjacent reinforcing lamellae over a relatively small distance. Forobtaining such arrangements, the slots in the row are constructedcorrespondingly.

In order to obtain, for instance, very thin sheets of high andrelatively balanced strength, the sheet material of reinforcing lamellaeand flexible filling lamellae can with advantage be biaxiallymolecularly oriented. Biaxially oriented film material normally exhibitshigh tensile strength but extremely low tear propagation resistance.However, it has proved that the product according to this embodiment ofthe present invention provides a surprising improvement of tearpropagation resistance.

Still higher tear propagation resistance is obtained when the lamellaeof the reinforcement. material have a predominant direction of molecularorientation and the sheet is laminated to another sheet having adifferent predominant direction of orientation. Preferably, the lastmentioned sheet should also be a sheet of oriented reinforcing lamellaeand flexible filling lamellae according to the invention.

The best results as regards as well tear propagation resistance as theoverall strength properties have been obtained with sheets of suchcross-laminated type, when the sheet or sheets in addition to theorientation in the predominant direction also have a substantialorientation in another direction. I herewith mean that the area of thesheet material should be drawn at a higher ratio than the ratio ofincreasing any of the linear dimensions during the orientation. Saidratios can be detected in the end product by means of X-ray defractiontechnique.

The sheet of oriented reinforcing lamellae and tiexible filling lamellaemay with advantage be made from highdensity polyethylene as thereinforcing material, as this polymer is cheap and technically suitable.The corresponding filling material may, for instance, be a copolymerbetween ethylene and vinyl-acetate, which is suitable for establishing anonsticky sealable layer.

Alternatively the reinforcing material may with advantage consist ofisotactic or syndiotactic polypropylene, whereas the corresponding llingmaterial may, for instance, be a block-copolymer having segments ofpolypropylene and `segments of randomly co-polymerizedethylene/propylene. Other suitable combinations for any particularpurpose can easily be selected by an expert.

The invention will now be described with reference to the accompanyingdrawings. In these:

FIG. 1 is a section through the extruded sheet material transverse tothe continuous dimension of the lamellae (or the continuous dimension ofthe rows of chopped lamellae), showing lamellae of flattened S-form.

FIG. 2 is a similar section showing U-formed lamellae.

FIG. 3 is a similar section showing the J-form of the reinforcinglamellae, resulting when the U is split already in connection with theextrusion of the lamellae, the sheet being shown before the actualcleavage.

FIG. 4 is a diagrammatic perspective view, partly in section, of a ringdie comprising a circular row of extrusion slots, and a collectingchamber ending with a slot for haul-off of the sheet, the device beingon principle adaptable to any of the forms shown in FIGS. 1, 2 and 3,but the figure showing slots for either S or U form and showing acollecting chamber `mainly for the S-form.

FIG. 5 is a diagrammatic section transverse to the collecting chambershown in FIG. 3, showing, however, a collection chamber suitable forobtaining the IU-form and further showing how lamellae are dragged intothis form.

FIG. 6 is a diagrammatic view from above of an apparatus as in FIG. 4,showing the drive and the emerging S-structure.

FIG. 7 is a representation of the slot arrangement for producing thestructure of FIG. 3.

FIG. 8 is a representation of the slot arrangement for producing on bothsides of the sheet a surface skin entirely consisting of the fillingmaterial.

FIG. 9 is a representation of the slot arrangement for producing a skinof a third material on both sides of a sheet consisting of crystalline,oriented lamellae and flexible filling lamellae.

In FIGS. l', 2 and 3, the film material is shown, for simplicity, asbeing made of solely two materials, 1 being the reinforcing material and2 being the filling material. For clarity, the lamellae are representedby lines, but in actual fact they have of course a thicknesscorresponding to the spacing of the full and dotted lines. Theirthickness and the angles to the plane of the sheet are grosslyexaggerated, as in fact the overall angle between the lamellae and thedimension of the sheet is below 2, and the thickn'ess of the reinforcinglamellae is in the range between 0.1 and 10p.. `In FIG. 3 it is furthershown that material 1 is absent in a layer in the core of the sheet,whereas material r2' is present all over.

The apparatus shown in FIG. 4 comprises a row of slots, three for thereinforcement material and four for the filling material, above which isa collecting chamber consisting of parts 5 and 6 which narrow down to anextrusion slot. The two parts of the collecting chamber may be rotatedtogether relative to the row of slots so that the drag exerted by thebottom of the collecting chamber on the lamellae 1 and 2 as they areextruded from slots 5 and 6 causes the lamellae to be laid substantiallyfiat along the row. Simultaneously, however, the lamellae are forcedupwards by fresh polymeric material being extruded through the slots andas they are forced uplwards their sides drag against the sides of thecollecting chamber, as indicated in FIG. 5, and in particular againstthe neck 7 (not shown in FIG. 4), and the |U-form of FIG. 2 results.

However, as shown in FIG. 6, the two parts 5 and 6 of the collectingchamber may also be moved in opposite directions to exert a symmetricaldrag on the two sides of the lamellae, whereby the S-form is produced.For this purpose, the reduction of thickness Within the collectingchamber ought to take place less rapidly, and it is even possible tocarry out the process without said reduction.

Furthermore it is shown that this zone of shear (chamber parts 6 and 7)follows immediately after the row of slots. This too is a preferable,but with respect to the S-form not very essential feature, as in fact itis possible to obtain good results when the two sets of lamellae areextruded even into a relatively long chamber where no transversal shearis applied, from there advancing into the zone of shear (parts 5 and 6).

As is easily seen, mixed forms between the S and the U can also beproduced by suitably selecting the relative and absolute speeds of thetwo parts 5 and 6.

In FIG. 7, the slots for material 1 are split so that material 2 fromslots 4 will be smeared in between the two half-parts of the lamellaeof 1. This arrangement is preferably used in connection with the processfor making the U-form of the lamellae, which will, however, in this caseturn out in the split form, shown in FIG. 3, (the I form). It is notessential that the orifice parts 3 lie adjacent to each other in theform of a split slot. In fact they can be orifices dislocated from oneanother.

In similar marmer the arrangement of FIG. 8 will produce on both sidesof the sheet a skin solely consisting of material 2, extruded throughslots 4, whereas in FIG. 9 a skin is produced from the material extrudedthrough orifices 8.

`In the following examples, the indications of mel indexes refer to ASTMD1238-62T. t

In each of the examples the S form lamellae are produced by use of theapparatus shown in FIGS. 4 and 6.

EXAMPLE l Production of a sheet with high contents of an inorganicfiller for use as substitute of book-print paper.

Reinforcing material: high density polyethylene of melt index 0.2 (ASTMcondition E).

Filling material: 50% talc powder -l- 501% lorw density polyethylene ofmelt index 70 (ASTM condition E).

Proportion between reinforcement material and filling material about1.1.

The sheet material should be biaxially drawn at about C. at a ratio of1:2 in both directions. Thickness before drawing about 0.1 mm.

EXAMPLE 2 Production of a light and stiff expanded sheet for packagingpurposes.

Reinforcing material: an ethylene/vinyl-acetate copolymer with 5%vinyl-acetate. Melt index 0.3 (ASTM condition E).

Filling material: expandable polystyrene containing petrol ether asexpansion agent. Appearing to have about the same melt viscosity as thepolyethylene.

Adhesive component: a mixture between (a) the same polyethylene and (b)a polystyrene with small contents of copolymerized butadiene, melt index0.5 (same condition).

Ratio between reinforcing material and filling material about 1:1.

The expansion takes place during haul-off. Temperature of the circularslot: 120 C. (but higher temperature at the start of the run).

Blow ratio about 2:1. Weight of the final sheet: about 50 grams per sq.m. Density of the final sheet: about 0.1 kg. per liter.

The product has in particular a high folding strength.

EXAMPLE 3 Production of a wrapping material consisting of crystalline,oriented lamellae and flexible lamellae.

Reinforcing material: the same high density polyethylene as in Examplel.

Filling material: the same copolymer of ethylene as in Example 2.

Proportion between reinforcing material and filling material: 6:4.

A skin of the filling material is produced on both surfaces.

The sheet is biaxially drawn at about 100 C. at ratios of about 2.5 :1in both directions. It exhibits an improved tear propagation resistancecompared to normal biaxially drawn film material.

EXAMPLE 4 Instead of being drawn in balanced manner, the sheet ofExample 3 is cross-drawn at ratio 1.5 :1 and simultaneously length-drawnat ratio 3:1 at about 100 C. The drawing can take place by means of atenter frame. Another unoriented sheet of Example 3 is cross-drawn atratio 3:1 and simultaneously length-drawn at ratio 1.5 1.

The two plies are laminated between nip-rollers, the temperature of therollers being kept at 80 C. and vapors of toluene being appliedtocondense into the nip on the sheet surfaces in order to bind the pliestogether.

The product exhibits improved tear propagation strength compared to anormal cross-laminate.

EXAMPLE 5 Production of a textile web.

1Reinforcing material: polycaprolactame of melt index 2.2 (ASTMcondition K) blended with polyethylene of melt index 7 (ASTM conditionE) in a planetary extruder. Ratio of polyamide to polyethylene: 75:25.

Filling material: The same components but ratio of polyamide topolyethylene: 55 :45.

The shear action should be adjusted to produce layers of an overallthickness of about 2,1 to equal the average diameter of the crystalwhiskers formed on crystallization of such molten polymer in polymermixtures when the latter are in drawn state during crystallization.

Blow ratio: 1:1.

Cooling during haul-off: strictly controlled air cooling, hot air beingused to keep the temperature of the sheet beyond 160 C. till all thepolyamide is crystallized. This temperature control has the purpose ofpromoting the growth of the whiskers.

The extruded sheet, having a thickness of about 70 microns, should bepassed through a bath of mineral oil for about 10 seconds and inimmediate succession hereto cross-drawn by means of a tenter frame,while keeping the temperature at 170 C. and allowing a lengthwisecontraction. Finally the oil shold be leached.

The product will be very suitable for many sanitary purposes, and aftercross-lamination of two plies of the material, the resultant productwill be suitable for disposable apparel. The uniting of the plies can becarried out by application of an elastomeric gluestuff in spots.

What I claim is:

1. An extruded sheet material. comprising a reinforcing polymericmaterial and a filling material, in which both these materials arepresent in the sheet material in the form of interspersed intimatelyadhering thin lamellae, the former having an overall thickness between0.1 and 10 microns and traversing the flat dimension of the sheet at anoverall angle of less than 2 to the surfaces of the sheet.

2. A sheet material as in claim 1, in which said lamellae are I-shapedin cross-section.

3. A sheet material as in claim 1, in which said lamellae are continuousover one of the principal dimensional directions of the area of thesheet material.

4. A sheet material as in claim 1 in which said filling materialconsists of a powder of inorganic solid particles.

5. A sheet material as in claim 1, in which said filling material is acellular polymeric material.

6. A sheet material as in claim 1 in which each lamella of said fillingmaterial comprises a split fibre network and each lamella of saidreinforcing material comprises a split fibre network of higher strengthand lower average fibre fineness than that forming the lamellae of saidfilling material.

7. A sheet material as in claim 1, in which the lamellae of fillingmaterial extend beyond the lamellae of reinforcing material to form atleast one surface layer of the sheet, said filling material having alower melting range than said reinforcing material.

8. A sheet material as in claim 1, in which lamellae of a crystallinepolymeric material having a substantially lower melting range than thereinforcing material are interspersed with the lamellae of thereinforcing and filling materials adjacent at least one surface of thesheet and extend beyond both to from at least one surface layer 0f thesheet.

9. A sheet material as in claim 1, in which the polymer of saidreinforcing material is crystalline.

10. A sheet material as in claim 1 in which the lamellae of saidreinforcing material are molecularly oriented.

11. A sheet material as in claim 1 further comprising lamellae of atleast one further extrudable material interspersed with those mentionedin claim 1.

12. A sheet material as in claim 1 wherein said further extrudablematerial consists of :an adhesive compatible with said reinforcing andfilling materials.

13. A sheet material as in claim 1, in which said filling materialincludes a polymer different from said reinforcing polymeric materialand said adhesive comprises a mixture of the polymers of saidreinforcing and filling materials.

14. A sheet material as in claim 1, in which said reinforcing materialconsists of polyethylene and said filling material consists of cellularpolystyrene, the two materials being united through interposed lamellaeof adhesive material.

References Cited UNITED STATES PATENTS 1,434,157 10/ 1922 Schuster161-69X 1,675,642 7/ 1928 Clewell 161-34UX 2,371,349 3/1945 Norton161-34UX 2,618,019 11/1952 Orsini 161-36X 2,879,547 3/1959 Morris161-189 3,101,848 8/1963 Heasley 161-168UX 3,236,373 2/1966 Lux l61-34UX3,481,663 12/ 1969 Greenstein 16 1-3 4X ROBERT F. BURNETT, PrimaryExaminer W. A. POWELL, Assistant Examiner U.S. C1. X.R.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Dated December l5,1970 Patent NO 3:547176]- Invent0r(5) Ole-Bendt RASMUS SEN It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as show-n below:

Claim 13, line l, change Claim l2,

signed arxid sealed this 20th day of July 1971.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. WILLIAM E. SCHUYLER, JR. Attesting OfficerCommissioner of Patents line l, change "claim l" to Claim ll

